油藏模型网格粗化的理论与方法

近20 年来, 由于油藏描述与油藏模拟的需要, 人们提出了许多油藏模型网格粗化(Reservoir Upscaling) 的理论与方法。这些方法大致可归纳为5 类: 指数律平均法、重正规化技术、解压力方程法、矢量法和拟函数法。传统方法的共同点是它们倾向于抹平一些在空间分布的渗透率极值条带, 例如, 泥岩夹层和裂缝。然而, 非均质油藏的生产实践和模拟实验都表明, 这些渗透率极值条带对原油采收率, 尤其是无水采收率影响极大。因此, 在网格粗化过程中怎样处理渗透率极值条带, 怎样对天然裂缝油藏以及石灰岩油藏进行网格粗化, 是这一研究领域有待解决的挑战性问题。     

油藏模型网格尺度对油藏模型精度的影响

油藏模型是利用计算机通过三维网格来再现油藏的地下实际地质状态和参数的,在油藏资料覆盖程度和分辨率一定的条件下,网格尺度要有一个适度的选择。利用油藏数值模拟技术分析了不同网格尺度对油藏模型精度的影响,认为网格步长过大,油藏模型将不能正确展示油藏资料表现油藏地下实际状态的程度,过小则只能增加工作量和研究周期,对提高油藏认识程度并无实质性意义。     

网格粗化技术对油藏数值模拟的影响

如何将密集的网格数据合理地转换到较粗的网格上去,这是现代油藏模拟技术的一个重要研究内容。在前人研究基础上,引入平均误差公式,从属性粗化和网格尺寸粗化两方面探讨了网格粗化技术对油藏数值模拟的影响。基于三微数值解的流动法优于其它的粗化方法,建议油藏数值模型的网格步长设为30~50m。进一步完善了网格粗化应遵循的基本步骤。     

从岩心模型到模拟模型尺度的有效扩展：地质模型的网格粗化方法

因为油藏的数据信息是从此油藏模拟网格更细小的尺度上得到的。所以网格粗化是必要的。本文由三个主题来讨论模型网格尺度的有效扩展：１对建立模拟模型和等级模型的回顾。２评价单相和两相流的简单平均方法对力求主解网格扩展技术的有效性。３流速依赖相对渗透率快速网格扩展法。从理论上讲，人们可以按取芯尺度来建立油藏模型。为了应用这个模型，人们需要通行网格尺度扩展以适用于各种类型的模拟研究。应当产生对油藏性质有代表性     

网格粗化混相处理新技术的发展和应用

为了更好地设计和管理混相注气，需要快速而精确的粗尺度混相模拟能力。在本文中，我们发表了初次接触混相驱替网格粗化新技术。该方法由两部分组成：有效通量边界条件（EFBC）和具有网格粗化相对渗透率方案的扩展Todd—Longstaff技术（ETLU）。前者近似解释了全流动场对局部网格粗化问题的影响，而后者修改了计算有效流体性质和粗化相对渗透率的方法，因此合理地描述了剩余油。 对部分分层的合成二维渗透率场来说，这项技术显示出在复制标准细尺度解法方面是成功的。该方法显示出在很宽的粗化倍数范围内都比其它网格粗化技术做得更好。然后将网格粗化程序应用于混相注气现场研究的三维模拟。还把一种近井网格粗化技术综合到了该方法中。我们认为，新方法提供了紧密地匹配标准解法的粗尺度模拟结果。另外，这项技术显示出在计算方面效率很高。     

胜坨油田坨21块油藏数模粗化算法及网格优化研究

目前大多数油藏的剩余油油藏数值模拟显示,剩余油主要存在于油田边部、渗透率较低的层以及井网不完善的区域,因为这些区域的剩余油面积大,在大尺度粗化网格下也容易刻画;而在油藏中部剩余油富集量少、分布面积小,甚至不明显。研究首先通过对9种不同粗化算法对最终开发效果影响分析,认为线性流动边界算法误差最小。通过模拟网格的优化,选择采用剩余油面积的1/9作为网格大小进行剩余油模拟研究,该网格既可以满足高含水期剩余油分布模拟需要,又大大降低计算时间。     

指示模拟前沉积微相的粗化方法研究

在油藏描述过程中,建立沉积微相模型会产生庞大的网格数据体,无法直接用于指示模拟,需对网格进行粗化处理。本文中以具体区块为例,选取不同的方法对进行指示模拟前的沉积微相进行粗化,并对各种方法所得的结果进行优劣分析。     

适于蒸汽辅助重力泄油开发的网格粗化技术

风城油田超稠油油藏蒸汽辅助重力泄油(SAGD)开发技术已逐步完善,但油藏工程研究环节仍面临常规网格粗化后信息损失量大的问题,尤其是对井轨迹偏移考虑不充分和薄隔夹层信息丢失,导致数值模拟结果精度不高,影响现场操作政策的制定,制约着SAGD的稳产高产。依据SAGD生产影响因素筛选关键信息,分析网格粗化算法、网格边界、网格尺寸对数值模拟的影响;利用Petrel软件进行网格粗化,对粗化模型进行验证;针对关键部分的信息缺失,借助数值模拟软件CMG的局部网格加密与网格属性回归来修正粗化模型,精细还原薄夹层。以此方法建立的油藏数值模型,在保障精度的同时提升了计算速度。以模型验证为控制手段,三维控制网格与二元叠合属性回归相结合的模型粗化技术,为精细地质模型与油藏数值模拟成功接口奠定了基础。     

储层地质模型与油藏模拟模型之间的桥梁——一种有效的模型粗化方法

针对油田储层地质模型向油藏模拟模型转化中粗化软件存在的问题，提出了一种实用的网格粗化方法，并编制了模型粗化程度，还给出了检验粗化结果的5个要点。应用效果表明，该粗化方法是有效的，它较好地解决了地质模型与油藏模型之间的转化问题。     

储层地质模型与油藏模拟模型之间的桥梁——一种有效的模型粗化方法

针对油田储层地质模型向油藏模拟模型转化中粗化软件存在的问题 ,提出了一种实用的网格粗化方法 ,并编制了模型粗化程序 ,还给出了检验粗化结果的 5个要点。应用效果表明 ,该粗化方法是有效的 ,它较好地解决了地质模型与油藏模型之间的转化问题     

Major Challenges for Reservoir Upscaling

Abstract

In the past two decades, many upscaling procedures have been proposed. The major methods are power-law average, renormalization technique, pressure-solver method, tenser method, and pseudo-function technique. The common problem of conventional upscaling methods is that they tend to smear out the spatially continuous extremes, such as shale barriers and open fractures. However, experience and previous simulation work in heterogeneous reservoirs have shown that oil recovery (especially water breakthrough oil recovery) mainly depends on the spatial connectivity of the extreme permeability values.

Lasseter et al. (1986) Lasseter, T. J., Waggoner, J. R. and Lake, L. W. 1986. “Reservoir heterogeneities and their influence on ultimate recovery.”. In Reservoir characterization Edited by: Schatzinger, R. A. and Jordan, J. F. 545Orlando: Academic Press, Inc..  [Google Scholar] proposed that scale-up of properties should be done from the scale of a representative elementary volume (REV), a volume for which the measured property does not change with an increase in scale over a given limit of scale. The notion of REV is physical-model oriented and proposed a criterion for upscaling technique. However, the decisive factor in upscaling is the grid system rather than individual physical point.

This article concludes that how to obtain REV for real system, how to evaluate the upscaling results quantitatively, how to treat extremes of permeability, as well as how to perform upscaling for naturally fractured reservoirs and carbonate reservoirs are the remained major challenging problems in this area. It is concluded that a great effort should be made on how to obtain the REV grid, which could best describe the heterogeneity of given reservoir at a given scale. Secondly how to perform the upscaling of all properties based on the REV grid is also a critical aspect and should be considered according to the different extent and pattern of heterogeneity of the original geological model respectively.     

REV Grid Technique for Reservoir Upscaling

Lasseter et al. (Lasseter, T. J., Waggoner, J. R., Lake, L. W. (1986). Reservoir Heterogeneities and Their Influence on Ultimate Recovery. Reservior Characterization, Orlando, Florida: Academic Press Inc., 545.) proposed that scale-up of properties should be done from the scale of a representative elementary volume (REV), a volume for which the measured property does not change with an increase in scale over a given limit of scale. The notion of REV has been a quite argued concept owing to its definition is not unequivocal, and it did not address how to obtain it in real system, some people even argue if REV really exists. Qi et al. (Qi, D., Wong, P. M., Liu, K. (2001). An improved global upscaling approach for reservoir simulation. Petroleum Science and Technology 19(7-8):779-795.) based on REV concept, proposed the new idea of REVG (representative elemental volume grid). This article further developed this idea, and based on it, proposed the REV grid upscaling technique. This new technique uses an algorithm, which is a combination of two-procedure-upgridding with reverse stepwise approach, it is a field-oriented 3D model. The new method concentrates on constructing a unique coarse grid, referred to as pseudo-REVG, which could best describe the heterogeneity of the original model at given scale. Mathematically, the variance of properties in REVG is the smallest within each block, and largest between the blocks. The proposed method is applied to two case studies, one of them is a 3D multiphase real reservoir, and the flow simulation results show that the consistency of the reservoir behavior before and after upscaling with REV grid technique is excellent. It is much better than that of the conventional upscaling methods.     

REV Grid Technique for Reservoir Upscaling

Abstract

Lasseter et al. (Lasseter, T. J., Waggoner, J. R., Lake, L. W. (1986 Lasseter, T. J., Waggoner, J. R. and Lake, L. W. 1986. Reservoir Heterogeneities and Their Influence on Ultimate Recovery. Reservoir Characterization 545Orlando, FL: Academic Press Inc..  [Google Scholar]). Reservoir Heterogeneities and Their Influence on Ultimate Recovery. Reservior Characterization, Orlando, Florida: Academic Press Inc., 545.) proposed that scale-up of properties should be done from the scale of a representative elementary volume (REV), a volume for which the measured property does not change with an increase in scale over a given limit of scale. The notion of REV has been a quite argued concept owing to its definition is not unequivocal, and it did not address how to obtain it in real system, some people even argue if REV really exists. Qi et al. (Qi, D., Wong, P. M., Liu, K. (2001 Qi, D., Wong, P. M. and Liu, K. 2001. An improved global upscaling approach for reservoir simulation. Petroleum Science and Technology, 19(7–8): 779–795. [CROSSREF][Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). An improved global upscaling approach for reservoir simulation. Petroleum Science and Technology 19(7–8):779–795.) based on REV concept, proposed the new idea of REVG (representative elemental volume grid). This article further developed this idea, and based on it, proposed the REV grid upscaling technique. This new technique uses an algorithm, which is a combination of two-procedure-upgridding with reverse stepwise approach, it is a field-oriented 3D model. The new method concentrates on constructing a unique coarse grid, referred to as pseudo-REVG, which could best describe the heterogeneity of the original model at given scale. Mathematically, the variance of properties in REVG is the smallest within each block, and largest between the blocks. The proposed method is applied to two case studies, one of them is a 3D multiphase real reservoir, and the flow simulation results show that the consistency of the reservoir behavior before and after upscaling with REV grid technique is excellent. It is much better than that of the conventional upscaling methods.     

An Improved P-Normal Transformation Approach in Reservoir Upscaling

Abstract:

In reservoir upscaling, in order to avoid small value dominance, p-normal the original data is necessary. The conventional type-curve approach to estimating p for p-normal transformation needs some manual work to type the curves. Also, its algorithm shows some considerable bias error. In this paper, the p-normal transformation techniques will be explored mainly in a reservoir engineer's point of view. Thereby, an improved p-normal transformation approach is presented. Its algorithm specially suits the transformation of permeability and porosity data fields. Furthermore, it could automatically be conducted together with the upscaling program. Test examples show that the improved method is more convenient to use than the type-curve approach in reservoir upscaling.     

An Improved P-Normal Transformation Approach in Reservoir Upscaling

In reservoir upscaling, in order to avoid small value dominance, p-normal the original data is necessary. The conventional type-curve approach to estimating p for p-normal transformation needs some manual work to type the curves. Also, its algorithm shows some considerable bias error. In this paper, the p-normal transformation techniques will be explored mainly in a reservoir engineer's point of view. Thereby, an improved p-normal transformation approach is presented. Its algorithm specially suits the transformation of permeability and porosity data fields. Furthermore, it could automatically be conducted together with the upscaling program. Test examples show that the improved method is more convenient to use than the type-curve approach in reservoir upscaling.     

考虑地质约束的储层非均质渗透率预测方法

储层各项物理参数在三维空间分布的定量描述是同藏地质模型研究的核心内容，渗透率是诸项物理参数中最重要也是定量描述的参之一，以分形技术为基础，以变序技术，局部权技术，相映技术为配套技术，对一个开发区块多口井的储层非均质渗透率地预测。     

Flexible Unstructured Flow-Based Gridding for Reservoir Coarse Scale Modeling

Discretization of spatial domain is a key step in valid upscaling and coarse scale dynamic modeling. The authors present a new procedure for flow based coarse scale gridding is introduced. Key flow paths are revealed quantitatively as an element size indicator by use of streamline and time of flight concept. Furthermore a new procedure to convert the results into a high-resolution element size map is presented. This elements size map guides powerful unstructured mesh generation algorithms to discretize the spatial domain. Fine-scale simulations results are compared with coarse scale ones for a series of water flooding examples to investigate the efficiency and accuracy of presented method. The results shows that apply of mentioned procedure for nonuniform gridding enhance the prediction behavior accuracy of simulations in compare to uniform gridding.     

碳酸盐岩储层流体性质识别新技术

碳酸盐储层由于其孔隙度低、非均质性强等原因，使得以电阻率高低来识别储层流体性质的常规方法失效。提出了不依赖于电阻率测井识别流体性质的新思路、新概念、新技术，包括核磁振测井的移谱、差谱技术；交叉多极阵列声波测井的体积压缩系以及补偿中子测井的长短计数率比值等技术。综合应用这些技术建立了一种新型的碳酸盐岩储层流体性质评价系统。该系统在大港油田千米潜山10多口井中取得了较好的地质效果。     

三元复合驱采出水对回注地层渗透率适应性研究

在超过 1年的时间内从大庆采油二厂三元复合驱试验区中心油井多次取采出水样并分析水样中化学剂质量浓度 ,聚合物在 71～ 381mg L范围 ,NaOH在 190～ 1197mg L范围 ,表面活性剂 (植物羧酸盐 )在 86～ 1197mg L范围。用Coulter激光粒度分析仪测定 ,在自然沉降的和沉降后又经滤纸过滤的共计 4个采出水样中 ,悬浮物总体积远大于未过滤清水 ,颗粒粒径平均值和中值也大于未过滤清水 ;一个采出水样的粒度分布曲线表明 ,未过滤水样中粒径分布范围为 0 .82 5～ 2 6 .2 9μm ,>15 μm的占很大比例 ,滤纸过滤可以除去大部分大粒径颗粒。将采出水样注入不同渗透率的石英砂胶结岩心 ,从注入压力 注入量曲线求得不产生严重堵塞的岩心最低渗透率为 2 5 0× 10 - 3μm2 。用压汞法测得的人造和天然岩心孔隙半径中值与渗透率的关系进行校正 ,得到回注三元复合驱采出水的地层渗透率应不低于 10 0× 10 - 3μm2 。图 3表 3参 2。